Transmission line transformers

ABSTRACT

A transmission line transformer having a time delay network having a signal terminal and a pair of output terminals connected to the signal terminal through a corresponding one of a pair of time delay elements, the delay line elements having different time delays. A pair of transmission lines, each one having a pair of electrically coupled elements. A first one of the elements in one of the transmission lines has a first end connected to one of the pair of output terminals. A second one of the elements in such one of the transmission lines has a second end connected to a second end of one of the pair of elements in the other one of the transmission lines. The first one of the pair of elements in the other one of the pair of transmission lines is coupled to a second one of the pair of output terminals.

TECHNICAL FIELD

This disclosure relates generally to transmission line transformers andmore particularly to transmission line transformers for impedancetransformation and balun applications.

BACKGROUND

As is known in the art, in many applications it is desired to transforman output impedance from an impedance, Z₀ to different impedance KZ₀,where K is an integer greater than 1. One device used to perform thisimpedance transformation is an impedance transformer. One type ofimpedance transformer uses concepts described in U.S. Pat. No.2,700,129, inventor G. GUANELLA issued Jan. 18, 1955; sometimes referredto an a Guanella transformer. Another type of impedance transformer is aRuthroff transformer; see a paper entitled “Some Broad-BandTransformers” by C. L. RUTHROFF, Proceedings of the IRE August 1959. Thebasic building block of the Guandella transformer, shown in FIG. 1A,includes: a pair of transmission lines, TL₁, TL₂ each one of thetransmission lines having a pair of electrically coupled elements, C₁,C₂ here shown schematically as a pair of mutual inductively coupledcoils, C₁, C₂. A first one of the coupled elements C₁ in a first one ofthe pair of the transmission lines TL₁ has a first end E₁ connected toan input terminal (IT) of the transformer and a second end E₂ coupled toa first output terminal (OT1) of the transformer. A second one of thecoupled elements C₂ in the first one of the pair of transmission linesTL₁ has a first end E₁ connected to a reference terminal (RT), heresystem ground, and a second end E₂ connected to a second end E₂ of afirst one of the pair of coupled elements C₁ in a second one of the pairof transmission lines TL₂. The first one of the pair of coupled elementsC₁ in the second one of the pair of transmission lines TL₂ has the firstend E₁ connected to the input terminal (IT). The second one of theelements C₂ of the second one of the pair of transmission lines TL₂ hasa first end E₁ connected to the reference terminal RT and a second endE₂ connected to a second output terminal OT2, which may be groundpotential. Ideally, voltages are applied between the coupled elementsC₁, C₂ in each transmission line TL₁, TL₂, and the transmission linesTL₁, TL₂ are interconnected together as shown to transform the inputimpedance Z₀ at the input of the transformer to an output impedance 4Z₀.It is noted that at high frequency applications, such as in microwavefrequency applications, the transmission line TL₁ and TL₂ may be coaxialtransmission lines, as shown in FIG. 1B. Here, the coupling elements C₁,and C₂ are the inner and outer conductors C₁ and C₂, respectively, ofthe coaxial transmission line. Here the input, or first ends E₁ of theinner conductors C₁ are connected to the input terminal IT and theinput, or first, ends E₁ of the outer conductors C₂ are connected to thereference terminal RT. The output, or second end E₂ of the innerconductor C₁ of transmission line TL₁ is connected to the first outputterminal OT1 and the second end E₂ of the outer conductor C₂ of thesecond transmission line TL₂ is connected to the second output terminalOT2. The second end E₂ of the outer conductor C₂ of the firsttransmission line TL₁ is connected to the inner conductor C₁ of thesecond transmission line TL₂, as shown. It is also noted that the basicbuilding block can be used to form other networks such as baluns.

This basic building block can be multiplied and arranged to providehigher impedance transformers. For example, a 5:1 Guanella impedancetransformer providing a 25Zo impedance transformation (where Z₀ is theinput impedance of the transformer) is shown in FIG. 1C. Here, theGuanella impedance transformer is fed by an amplifier having an outputimpedance Z₀. The output of the amplifier is fed to a 5:1 power divideror splitter having here, in this example, five output coupled to theinputs of five transmission lines, TL₁-TL₅, respectively, hererepresented as a pair of mutually inductively coupled coils, C₁, C₂.More particularly, the upper one of coils, C₁, in each one of thetransmission lines TL₁-TL₅ has an input, or first, end E₁ connected tothe output of the amplifier and the lower one of the coils, C₂, in eachone of the transmission lines TL₁-TL₅ has an input, or first, end E₁connected to system ground. The output, or second, end, E₂, of the lowercoil, C₂ in transmission line TL₁ is connected to an output end E₂ ofthe upper coil C₁ in the next one of the transmission lines, heretransmission line TL₂; the second end, E₂, of the lower coil, C₂ intransmission line TL₂ is connected to an output end E₂ of the upper coilC₁ in the next one of transmission line, here transmission line TL₃; thesecond end, E₂, of the lower coil, C₂ in transmission line TL₃ isconnected to an output end E₂ of the upper coil C₁ in the next one ofthe transmission line, here transmission line TL₄; the second end, E₂,of the lower coil, C₂ in transmission line TL₄ is connected to an outputend E₂ of the upper coil C₁ in the next one of the transmission lines,here transmission line TL₅. The second output end E₂ of the upper coilC₁ of transmission line TL₁ provides an output terminal of the Guanellaimpedance transformer and the second output end E₂ of the lower coil C₂of transmission line TL₅ is connected to system ground, as shown. Thefive outputs of the power divider are in-phase with each other, that is,they have the same electrical length or time delay from the output ofthe amplifier to the first end E1 of each the upper one of coils, C₁, ineach one of the transmission lines TL₁-TL₅. With such an arrangement,the voltage produced across the outputs ends E₂ of coils C₁, C₂ of eachof the transmission lines, TL₁-TL₅ will be V₁-V₅, respectively, asindicated. See also, for example: U.S. Pat. No. 7,495,525, issued Feb.24, 2002, Ilkov et al.; U.S. Pat. No. 6,756,874, Buckles et al., issuedJun. 29, 2004 and, Power Combiners, Impedance Transformers andDirectional Couplers by Andrei Grbeanikov, December 2007 High FrequencyElectronics Copyright © 2007 Summit Technical Media, LLC.

Further, by properly adjusting, or minimizing, the time delays(T_(D1)-T_(D5)) of the connections (in effect the length of theconnectors) between the second ends E₂ of one of the transmission linesto second end E₂ of the next one of the transmission lines,V_(IN)=V₁=V₂=V₃=V₄=V₅ and thus, the output voltage of the transformer is5*V_(IN). The current I_(IN) is split equally among the ends E₁ of coilsC₁ of TL₁ thru TL₅ such that each currentI₁=I₂=I₃=I₄=I₅=I_(OUT)=I_(IN)/5. As a result, the output impedance ofthe amplifier, Z_(0,IN)=V_(IN)/I_(IN), will be transformed by theGuanella impedance transformer to output impedanceZ_(0,OUT)=V_(OUT)/I_(OUT)=(5*V_(IN))/(I_(IN)/5)=25Z_(0,IN). In many highfrequency applications, such as in microwave applications, thetransmission lines are coaxial transmission lines, as shown in FIG. 1D.FIG. 1D shows a coaxial transmission line implantation of the 5:1Guanella impedance transformer shown in FIG. 1C. In order to improveperformance, primarily bandwidth, the coaxial transmission lines areenclosed in a ferrite core, not shown. The real world implementation ofthe transformer is impaired by certain real-world features in itslayout; namely the above-mentioned time delays developed in the linesconnecting the transmission line sections to one another.

SUMMARY

In accordance with the disclosure, a transmission line transformer isprovided having a time delay network. The time delay network includes apair of output terminals connected to an input terminal through acorresponding one of a pair of time delay elements, each one of the timedelay elements having a different time delay. The transmission linetransformer includes a transmission line section having a pair oftransmission lines, each one of the transmission lines having a pair ofelectrically coupled elements. A first one of the electrically coupledelements in each one of the pair of transmission lines has a first endconnected to a corresponding one of the pair of output terminals of thetime delay network. A second one of the electrically coupled elements ina first one of the transmission lines has a second end connected to asecond end of the first one of the pair of electrically coupled elementsin a second one of the pair of transmission lines.

In one embodiment, a second end of the first electrically coupledelement of said first of the pair of transmission lines is connected toan output of the transmission line transformer.

In one embodiment, one end of the second electrically coupled element insaid second one of the pair of transmission lines is connected to areference terminal of the transmission line transformer.

In one embodiment, a first end of the second electrically coupledelement in said first of the pair of transmission lines is connected tothe reference terminal.

In one embodiment, a first end of the second element in said second oneof the transmission lines is connected to the reference terminal.

In one embodiment, a transmission line transformer is provided having: atime delay network having: a first input terminal connected to a signalterminal; a second input terminal connected to a reference terminal; anda pair of output terminals, each one of the pair of output terminalsbeing connected to the input terminal through a corresponding one of apair of time delay elements, each one of the time delay elements havinga different time delay, a pair of transmission lines, each one of thetransmission lines having a pair of electrically coupled elements. Afirst one of the electrically coupled elements in a first one of thepair of the transmission lines has a first end connected to a first oneof the pair of output terminals of the time delay line network and asecond end coupled to a first one of the output terminals of thetransmission line transformer. A second one of the electrically coupledelements in the first one of the pair of transmission lines has a firstend connected to the reference terminal and a second end connected to asecond end of a first one of the pair of electrically coupled elementsin a second one of the pair of transmission lines. The first one of thepair of electrically coupled elements in the second one of the pair oftransmission lines is coupled to a second one of the pair of outputterminals of the time delay network.

In one embodiment, a transmission line transformer is provided having: atime delay network having a pair of output terminals connected to aninput terminal through a corresponding one of a pair of time delayelements, each one of the time delay elements having a different timedelay, and a transmission line section comprising a pair of transmissionlines. Each one of the transmission lines includes a pair ofelectrically coupled elements, each one of the pair of electricallycoupled elements having an input end and an output end. A first one ofthe electrically coupled elements in each one of the pair oftransmission lines has the input end thereof connected to acorresponding one of the pair of output terminals of the network. Thefirst one of the electrically coupled elements in the first one of thepair of transmission lines has the output end thereof connected to afirst output terminal of the transmission line section. A second one ofthe electrically coupled elements in the first one of the transmissionlines has the output end thereof connected to the output end of thefirst electrically coupled element of a second one of the pair oftransmission lines. The output end of the second one of the electricallycoupled elements in the second one of the transmission lines isconnected to a second output terminal of the transmission line section.The time delay element of each one of the pair of time delay provides adifferent predetermined time delay selected to produce a voltage betweenthe output end of the first one of the electrically coupled elements inthe first one of the pair of transmission lines and output end of thesecond one of the pair of transmission lines equal to, and in phasewith, a voltage produced between the output end of the first one of theelectrically coupled elements in the second one pair of transmissionlines and the output end of the second one of the electrically coupledelements in the second one of the pair of transmission lines.

In one embodiment, the network includes a pair of amplifiers, each oneof the pair of amplifiers being serially connected to a correspondingone of the pair of time delay elements.

With such an arrangement, time delays are independently selected ratherthan distributing the input signal through equal delays to thetransmission lines from a single port. Thus, to compensate the timedelays in interconnecting the transmission lines on the output of thetransmission line transformer, the transmission line transformer inputside is driven through an independently selectable compensating timedelay. More particularly, the inventors have recognized that with suchan arrangement, time delays between interconnected transmission linesneed not be minimized; but rather may be compensated for by the timedelay network preceding the transmission line section. For example,during a calibration/testing or simulation procedure, after constructionof the transmission line section with the outputs of the transmissionlines thereof electrically interconnected one to the other, therequisite time delay from the first end of first one of the electricallycoupled elements in each one of the pair of transmission lines to theoutputs of the transmission line section is determined. Once determined,the time delay network is constructed with predetermined time delaysselected in accordance with the time delay determined during thecalibration/testing or simulation procedure.

The details of one or more embodiments of the disclosure are set forthin the accompanying drawings and the description below. Other features,objects, and advantages of the disclosure will be apparent from thedescription and drawings, and from the claims.

DESCRIPTION OF DRAWINGS

FIG. 1A is a schematic diagram of a building block used in atransmission line transformer, according to the PRIOR ART;

FIG. 1B is a schematic diagram of a building block used in atransmission line transformer with coaxial transmission lines, accordingto the PRIOR ART;

FIG. 1C is a schematic diagram of a 5:1 Guanella impedance transformerusing the building block of FIG. 1A, according to the PRIOR ART;

FIG. 1D is a schematic diagram of a 5:1 Guanella impedance transformerusing the building block of FIG. 1B;

FIG. 2 is a schematic diagram of a building block used in a transmissionline transformer, according to the disclosure;

FIG. 3 is a schematic diagram of a 5:1 Guanella impedance transformerusing the building block of FIG. 2, according to the disclosure;

FIG. 4 is a schematic diagram of a 5:1 Guanella impedance transformerusing the building block of FIG. 2 implemented with coaxial transmissionlines, according to the disclosure;

FIG. 5 is a diagrammatical plane view of the 5:1 Guanella impedancetransformer of FIG. 4, according to the disclosure;

FIG. 6 is a diagrammatical plane view of a transmission line sectionused in the 5:1 Guanella impedance transformer of FIG. 5 according tothe disclosure;

FIG. 6A is a cross sectional sketch of an enlarged portion of thetransmission line section of FIG. 6, such enlarged portion beingindicated by a circled region labeled 6A-6A in FIG. 6 according to thedisclosure; and

FIG. 6B is a plan view of an enlarged portion of the transmission linesection of FIG. 6, such enlarged portion being indicated by a circledregion labeled 6B-6B in FIG. 6 according to the disclosure;

FIGS. 6C-6E are cross-sectional views of enlarged portions of thetransmission line section of FIG. 6, such cross sections being takenalong lines 6C-6C, 6D-6D and 6E-6E, respectively in FIG. 6; and

FIG. 7 is an isometric sketch of the transmission line section of FIG. 6according to the disclosure.

Like reference symbols in the various drawings indicate like elements.

DETAILED DESCRIPTION

Referring now to FIG. 2, a transmission line transformer 10 is shownhaving: a time delay network 12 connected to an input terminal 14. Thetime delay network 12 includes: a signal terminal 16 connected to theinput terminal 14; a reference terminal 18, here system ground; and apair of output terminals 22 ₁, 22 ₂, each one of the pair of outputterminals 22 ₁, 22 ₂ being connected to the input terminal 16 through acorresponding one of a pair of time delay elements TD₁, TD₂, as shown.Each one of a pair of amplifiers AMP₁, AMP₂, is connected to acorresponding one of the pair of time delay elements TD₁, TD₂, as shown.

The transmission line transformer 10 includes a transmission linesection 23 having a pair of input ports 25 ₁, 25 ₂ connected to theoutputs of the pair of amplifiers AMP₁, AMP₂, respectively, as shown.The transmission line section 23 includes a pair of transmission lines,TL₁, TL₂ each one of the transmission lines TL₁, TL₂ having a pair ofelectrically coupled elements C₁, C₂, here shown as a pair of mutuallycoupled coils. A first one of the elements C₁ in a first one of the pairof the transmission lines, here transmission line TL₁ has a first end E₁connected to a first one of the pair of output terminals 22 ₁, 22 ₂,here output terminal 22 ₁ of the time delay line network 12 throughamplifier AMP₁ and a second end E₂ coupled to output terminal 28 of thetransmission line transformer 10. A second one of the elements C₂ in thefirst one of the pair of transmission lines TL₁ has a first end E₁connected to the reference terminal and a second end E₂ connected to asecond end E₂ of a first one of the pair of elements C₁ in a second oneof the pair of transmission lines TL₂ through a connector 32, as shown.The first one of the pair of elements C₁ in the second one of the pairof transmission lines TL₂ is coupled to the one of the pair of outputterminals 22 ₁, 22 ₂, here output terminal 22 ₂ of the time delaynetwork 12 through amplifier AMP₂, as shown. A second end E₂ of thesecond element C₂ of second one of the pair of transmission lines TL₂ isconnected to output 30 of the transmission line transformer 10, here tosystem ground. A first end E₁ of the second element C₂ in the second oneof the pair of transmission lines TL₂ is also connected to systemground, as indicated. A first end E₁ of the second element C₂ the secondone of the pair of transmission lines TL₂ is connected to the systemground, as shown. The delay lines TD1 and TD2 are selected so that thevoltage V₁ across the first transmission line TL₁ is equal to, and inphase with the voltage V₂ across the second transmission line TL₂. Inthat way, the output voltage across the output terminals 28, 30 equalsV₁+V₂; where V₁=V₂. As a result, the input impedance Z₀ of thetransmission line transformer 10 across terminals 25, 18 will betransformed to an output impedance 4Z₀ across output terminals 28, 30.

Referring now to FIG. 3, a transmission line transformer 10′ is shownhere arranged as a 5:1 Guanella impedance transformer. The transmissionline transformer 10′ includes a time delay network 12′. The time delaynetwork 12′ includes: an first input terminal 14 connected to a signalterminal 16; a second input terminal 18 connected to a referencepotential, here system ground; a plurality of N, where N is an integergreater than 1, here N=5 of time delay elements TD₁-TD₅; a plurality ofN output terminals 22 ₁, 22 ₅, respectively, each one of the five outputterminals 22 ₁-, 22 ₅ being connected to the input terminal 16 through acorresponding one of the five time delay elements TD₁-TD₅, respectively,as shown. The output terminals 22 ₁-, 22 ₅ are connected to acorresponding one of five amplifiers AMP₁-AMP₅, respectively, as shown.The outputs of the amplifiers output terminals 25 ₁-, 25 ₅ are connectedto a corresponding one of five amplifiers AMP₁ are connected to atransmission line section 23′, here including five transmission lines,TL₁-TL₅ each one of the transmission lines TL₁-TL₅ having a pair ofelectrically coupled elements C₁, C₂, here shown as a pair of mutuallycoupled coils. More particularly, the upper one of coils, C₁, in eachone of the transmission lines TL₁-TL₅ has a first, or input, end E₁connected to one of the output of the amplifier and the lower one of thecoils, C₂, in each one of the transmission lines TL₁-TL₅ has a first endE₁ connected to system ground. The second end, E₂, of the lower coil, C₂in transmission line TL₁ is connected to a second end E₂ of the uppercoil C₁ in the next one of the transmission lines, here transmissionline TL₂ through a connector 32 ₁; the second end, E₂, of the lowercoil, C₂ in transmission line TL₂ is connected to a second end E₂ of theupper coil C₁ in the next one of transmission line, here transmissionline TL₃ through a connector 32 ₂; the second end, E₂, of the lowercoil, C₂ in transmission line TL₃ is connected to a second end E₂ of theupper coil C₁ in the next one of the transmission line, heretransmission line TL₄ through a connector 32 ₃; the second end, E₂, ofthe lower coil, C₂ in transmission line TL₄ is connected to a second endE₂ of the upper coil C₁ in the next one of the transmission lines, heretransmission line TL₄ through a connector 32 ₄. The second end E₂ of theupper coil C₁ of transmission line TL₁ provides an output terminal ofthe Guanella impedance transformer and the second end E₂ of the lowercoil C₂ of transmission line TL₅ is connected to output terminal 30,here at system ground, as shown. With such an arrangement, the voltageproduced across the output terminals of each of the transmission lines,TL₁-TL₅ will be V₁-V₅, respectively, as indicated. The delay linesTD₁-TD₅ are selected so that the voltage V₁ across the first one of thetransmission lines TL₁ is equal to, and in phase with the voltage V₂across the second one of the transmission line TL₂; the voltage V₃across the third transmission line TL₃ is equal to, and in phase withthe voltage V₂ across the second transmission lines TL₂; the voltage V₄across the fourth transmission lines TL₄ is equal to, and in phase withthe voltage V₃ across the third transmission lines TL₃; the voltage V₅across the fifth transmission lines TL₅ is equal to, and in phase withthe voltage V₄ across the fourth transmission lines TL₄. In that way,the output voltage across the output terminals 28, 30 will equalV₁+V₂+V₃+V₄+V₅; where V₁=V₂=V₃=V₄=V₅, and the input impedance Z₀ of thetransmission line transformer 10′ across terminals 16, 18 will betransformed to an output impedance 25Z₀ across output terminals 28, 30.

Referring to FIG. 4, here the transmission line transformer 10′ of FIG.3 is shown implemented with coaxial transmission line TL₁-TL₅. It isnoted that the time delay elements TD₁-TD₅, may be placed either beforeor after the amplifiers AMP₁-AMP₅, respectively as indicated. A moredetailed description of the transmission line transformer 10′ of FIG. 5is shown. Thus, as shown, the time delay network 12′ is here amicrostrip transmission line circuit having a dielectric board 30 havinga ground plane conductor, not shown, on the bottom of the board 30 witha plurality of, here five strip conductors of different lengths to onthe top of the board 30 to provide the five time delay elements TD₁-TD₅.The outputs of the five time delay elements TD₁-TD₅ are coupled to acorresponding one of the five amplifiers AMP₁-AMP₅, as shown. Here, eachone of the five amplifiers AMP₁-AMP₅, is formed as a separate monolithicmicrowave integrated circuit (MMIC). That is, here each one of the fiveamplifiers AMP₁-AMP₅, is formed on a separate integrated circuit chip.

One method which may be used to determine the time delays TD1-TD5 is asfollows: During a calibration/testing or simulation procedure, afterconstruction of the transmission line section 23′ with the outputs ofthe transmission lines TL1-TL5 electrically interconnected one to theother as shown and as described above, the requisite time delay from thefirst end E1 of first one of the electrically coupled elements C1 ineach one of the transmission lines TL1-TL5 to the output 28 of thetransmission line section 23′ is determined. Once determined, the timedelay network 30 is constructed with the time delays TD1-TD5 having aproper physical length such that the time delays produce predeterminedtime delays determined during the calibration/testing procedure. It isnoted that time delays TD1-TD5 here, in this example, have differentelectrical lengths; however, the electrical lengths from the input port14 to the first ends E1 of the first elements C1 of the transmissionlines TL1-TL5 are proper to produce the proper output voltage across theoutput terminals 28, 30; that is V₁+V₂+V₃+V₄+V₅; where V₁=V₂=V₃=V₄=V₅,as shown in FIG. 3. The outputs of the five amplifiers AMP₁-AMP₅ are fedto the transmission line section 23′. The transmission line section 23′,shown in more detail in FIGS. 6 and 6A, includes a pair of microstriptransmission line sections 34, 36. Microstrip transmission line section34 includes a dielectric board 38 having a ground plane conductor, notshown, on the bottom of the board 38, a plurality strip conductors onthe top of the board 38 to provide the input ports 25 ₁-25 ₅, and aconductor 39 which is connected to a ground plane conductor 54 whichextends from the bottom of the board 38. Microstrip transmission linesection 36 includes a dielectric board 40 having a ground planeconductor, not shown, on the bottom of the board 40 with two stripconductor layers, one on the top of the board 40 and one embedded inboard 40. The top layer provides output port 28.

Disposed between the pair of microstrip transmission line sections 34,36 are the transmission lines TL₁-TL₅, here each one being a coaxialtransmission line having a pair of coupling elements. C₁, C₂, element C₁being the inner conductor of the coaxial transmission line and elementC₂ being the outer conductor of the coaxial transmission line. Each oneof the first ends E₁ of the elements C₁ is connected to a correspondingone of the input ports 25 ₁-25 ₅, and each one of the first ends E₁ ofthe elements C₂ is connect to the conductor 39. It is noted that theconductor 39 is electrically isolated from the input ports 25 ₁-25 ₅ bythe dielectric board 38, as shown more clearly in FIGS. 6 and 6A, whereFIG. 6A shows an exemplary one of the transmission lines TL₁-TL₅, heretransmission line TL₅. The second end E₂ of coupling elements C₁ oftransmission line TL₁ is connected to output port 28, as shown. Thesecond end E₂ of coupling elements C₂ of transmission line TL₁ isconnected to the second end E₂ of coupling element C₁ of transmissionline TL₂ by a conductor 32 ₁ disposed on the dielectric board 40. Thesecond end E₂ of coupling elements C₂ of transmission line TL₂ isconnected to the second end E₂ of coupling element C₁ of transmissionline TL₃ by a conductor 32 ₂ disposed on the dielectric board 40. Thesecond end E₂ of coupling elements C₂ of transmission line TL₃ isconnected to the second end E₂ of coupling element C₁ of transmissionline TL₄ by a conductor 32 ₃ disposed on the dielectric board 40. Thesecond end E₂ of coupling elements C₂ of transmission line TL₄ isconnected to the second end E₂ of coupling element C₁ of transmissionline TL₅ by a conductor 32 ₄ disposed on the dielectric board 40. Thesecond end E₂ of coupling elements C₂ of transmission line TL₅ isconnected to a conductor 41 on the top of dielectric 40; the conductor41 being electrically isolated from output port 28, and the conductors32 ₁-32 ₄ by portions of the dielectric board 40. Conductors 39 and 41are both connected to system ground. Here, the transmission lines TL₁and TL₂ are disposed within a hollow ferrite core 50 ₁ and transmissionlines TL₃ and TL₄ are disposed within a hollow ferrite core 50 ₂, asshown.

FIG. 6A shows the first end E1 of the coupling elements C₁ and C₂ of anexemplary one of the transmission lines TL₁-TL₅, here transmission lineTL₅. The first end E1 of coupling element C₁, here the center conductorof the coaxial conductor of transmission line TL₅ is connected inputport 25 ₅ of the transmission line section 23′ and the first end E1 ofthe coupling element C₂, here the outer conductor of the coaxialconductor of TL₅ is connected to conductor 54 on dielectrics board 38.It is noted that the center conductor, coupling element C1 is physicallyseparated by a dielectric 51 from the coupling element C₂; however atmicrowave frequencies the center conductor coupling element C₁ and outerconductor coupling element C₂ are electrically coupled by the electricfield of the microwave energy passing through the coaxial transmissionline. It is noted that the conductor 39 is electrically isolated fromthe port 25 ₅ by region 52. It is also noted that the ground planeconductor on the bottom of dielectric 38, mention above, is here shownas conductor 54 and is connected to conductor 39.

More details of the connections of the center conductor couplingelements C1 to the outer conductor coupling element C₂ of thetransmission lines TL1-TL5 are shown in FIGS. 6B through 6E. It is firstnoted that because the center conductor coupling elements C1 and theouter conductor coupling element C₂ are at two different elevations; thea dielectric board 40 is constructed has an upper portion 40U and alower portion 40L as indicated in FIG. 6B and that the connectors 32₁-32 ₄ each has two sections 32 a, 32 b; section 32 a being on top ofboard 40U and section 32 b being on board 40L, the two sections 32 a and32 b being electrically connected by conductive vias 32 c, as shown moreclearly in FIG. 6E. Thus, sections 32 a are connected to the centerconductor coupling elements C1; sections 32 b are connected to the outerconductor coupling element C₂ and the two are electrically connected bythe conductive vias 32 c. Also the outer conductor coupling element C₂of transmission line TL5 is connected to the ground plane conductor 54through a conductor 60 and conductive vias 62, as shown in FIG. 6D.

FIG. 7 is an isometric view of the transmission line transformer 10.

A number of embodiments of the disclosure have been described.Nevertheless, it will be understood that various modifications may bemade without departing from the spirit and scope of the disclosure. Forexample, in some applications, the ferrite cores need not be required.Further, the number of transmission line sections may be greater or lessthan 5. Accordingly, other embodiments are within the scope of thefollowing claims.

1. A transmission line transformer, comprising: a time delay networkhaving a pair of output terminals connected to an input terminal througha corresponding one of a pair of time delay elements, the delay lineelements having different time delays; a transmission line sectioncomprising a pair of transmission lines, each one of the transmissionlines having a pair of electrically coupled elements, a first one of theelectrically coupled elements in each one of the pair of transmissionlines having a first end connected to a corresponding one of the pair ofoutput terminals of the time delay network, a second one of theelectrically coupled elements in a first one of the transmission lineshaving a second end connected to a second end of the first one of thepair of electrically coupled elements in a second one of the pair oftransmission lines.
 2. The transmission line transformer recited inclaim 1 wherein a second end of the first electrically coupled elementof said first of the pair of transmission lines is connected to anoutput of the transmission line transformer.
 3. The transmission linetransformer recited in claim 2 wherein one end of the secondelectrically coupled element in said second one of the pair oftransmission lines is connected to a reference terminal of thetransmission line transformer.
 4. The transmission line transformerrecited in claim 3 wherein a first end of the second electricallycoupled element in said first of the pair of transmission lines isconnected to the reference terminal.
 5. The transmission linetransformer recited in claim 4 wherein a first end of the secondelectrically coupled element in said first one of the transmission linesis connected to the reference terminal.
 6. A transmission linetransformer, comprising: a time delay network having: an first inputterminal connected to a signal terminal; a second input terminalconnected to a reference terminal; and a pair of output terminals, eachone of the pair of output terminals being connected to the inputterminal through a corresponding one of a pair of time delay elements,the delay line elements having different time delays; a pair oftransmission lines, each one of the transmission lines having a pair ofelectrically coupled elements; wherein a first one of the electricallycoupled elements in a first one of the pair of the transmission lineshas a first end connected to a first one of the pair of output terminalsof the time delay line network and a second end coupled to a first oneof the output terminals of the transmission line transformer; wherein asecond one of the electrically coupled elements in the first one of thepair of transmission lines has a first end connected to the referenceterminal and a second end connected to a second end of a first one ofthe pair of electrically coupled elements in a second one of the pair oftransmission lines; and wherein the first one of the pair ofelectrically coupled elements in the second one of the pair oftransmission lines is coupled to a second one of the pair of outputterminals of the time delay network.
 7. A transmission line transformer,comprising: a time delay network having a pair of output terminalsconnected to an input terminal through a corresponding one of a pair oftime delay elements, the delay line elements having different timedelays; a transmission line section comprising a pair of transmissionlines, each one of the transmission lines having: a pair of electricallycoupled elements, each one of the pair of electrically coupled elementshaving an input end and an output end; wherein: a first one of theelectrically coupled elements in each one of the pair of transmissionlines has the input end thereof connected to a corresponding one of thepair of output terminals of the network; the first one of theelectrically coupled elements in the first one of the pair oftransmission lines has the output end thereof connected to a firstoutput terminal of the transmission line section; a second one of theelectrically coupled elements in the first one of the transmission lineshas the output end thereof connected to the output end of the firstelectrically coupled element of a second one of the pair of transmissionlines; and the output end of the second one of the electrically coupledelements in the second one of the transmission lines is connected to asecond output terminal of the transmission line section; and wherein thetime delay element of each one of the pair of time delay provides apredetermined time delay selected to produce: a voltage between theoutput end of the first one of the electrically coupled elements in thefirst one of the pair of transmission lines and output end of the secondone of the pair of transmission lines equal to, and in phase with, avoltage produced between the output end of the first one of theelectrically coupled elements in the second one pair of transmissionlines and the output end of the second one of the electrically coupledelements in the second one of the pair of transmission lines.
 8. Thetransmission line transformer recited in claim 7 wherein the networkincludes a pair of amplifiers, each one of the pair of amplifiers beingserially connected to a corresponding one of the pair of time delayelements.
 9. The transmission line transformer recited in claim 7wherein each one of the each one of the transmission lines is a coaxialtransmission line having a center conductor and an outer conductor, and;including a dielectric structure having a upper portion disposed above alower portion, with an electrical connector on the upper portion and anelectrical connector on the lower portion electrically interconnectedwith an electrically conductive via passing though the upper portion,and wherein the electrical connector on the upper portion iselectrically connected to the center conductor of one coaxialtransmission line and the electrical connector on the lower portion iselectrically connected to the outer conductor of another coaxialtransmission line.